Effectiveness of Vitamin D Supplementation on Disease Course in Inflammatory Bowel Disease Patients: Systematic Review With Meta-Analysis

Abstract Background The vitamin D role in bone metabolism is well known; however, recent evidence suggests the impact of vitamin D in immune modulation and its implications in immune-mediated diseases, including inflammatory bowel disease (IBD). Method We performed a systematic review with meta-analysis by a specific protocol (PROSPERO: CRD42022311184; March 2022, https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=311184). Randomized clinical trials involving IBD patients treated with vitamin D supplementation, compared with placebo, that evaluated the risk of clinical relapse and disease activity were included. Literature search was performed using Medline, Scopus, and Cochrane CENTRAL through January 2022. Results Out of 1448 articles, 12 (11 full-texts and 1 abstract) were included. Seven randomized clinical trials reported data on the clinical relapse as dichotomous outcome, while 7 studies reported data on disease activity expressed as continuous variables. The pooled risk ratio of clinical relapse was 0.64 (95% confidence interval, 0.46-0.89; I2 = 25%) among 458 IBD patients. However, this seems to be solid only in Crohn’s disease (CD) patients. In fact, only 2 studies, involving 67 patients with ulcerative colitis, were included in the analysis. CD patients in clinical remission had a strong significant risk reduction in clinical relapse (risk ratio, 0.47; 95% confidence interval, 0.27-0.82; I2 = 0%), suggesting that it could be a specific subgroup with maximum clinical benefit of vitamin D supplementation. Conclusions This meta-analysis shows that vitamin D supplementation can reduce the risk of clinical relapse in IBD patients, especially in CD patients in clinical remission. In a subgroup analysis, it was not significant (due to small number of studies and low number of patients), and well-powered studies are needed, in particular for ulcerative colitis patients.